Wrist detection and heart rate sensor acting up suddenly

I got my Apple Watch Series 2 in the beginning of January and had literally no problems with it until now. Ever since yesterday morning after a short domestic flight, the wrist detection is acting up. At first, I couldn't even unlock it by unlocking the iPhone, and it locked itself every time the screen turned off. At that time, I also tried to use the heart rate sensor and it reported numbers over 200. Turning it off and on again didn't help. After connecting it to power for a while, it kind of worked again, but it still locks itself randomly all the time.

So, do you think the sensor is broken in some way? I have warranty and Apple Care, so if it doesn't go away, I might have to replace it.